I started using one yesterday. The paper is pretty nice—a bit smoother than what you get with Field Notes, but it stands up well to all the fountain pen ink I have thrown at it so far.
The leatherette cover is interesting. I like the feel of it, but it remains to be seen how holds up to being carried around in my back pocket for a few weeks.
My only gripe so far is that the stitched binding is a little too stiff. I never had a problem with the staples Field Notes lying flat, but this notebook seems to want to close. I find I have to hold it flat more than I would like while writing in it.